Mold and method for increasing the rate of heat abstraction from a continuous casting



Aug. 25, 1970 M. R. MQORE 3,525,380

MOLD AND METHOD FOR INCREASING THE RATE OF HEAT ABSTRACTION FROM A CONTINUOUS CASTING Filed March 27, 1968 'll lll ll I l||ll| IN VE N T 0/? MICHAEL R. MOORE r I l/ Altar/1y United States Patent U.S. Cl. 16448 1 Claim ABSTRACT OF THE DISCLOSURE A non-uniform (i.e., converging or diverging) electric field of high intensity is applied across the air gap between a continuous casting and the mold in which it is formed, caused by contraction of the casting from the mold wall as a result of cooling. The mold is formed in two parts, an upper portion which is in contact with the continuous casting and therefore grounded, and a lower portion which is insulated from ground, charged to a high-voltage and separated from the continuous casting by the air gap. The non-uniform field between the lower mold portion and grounded continuous casting causes increased movement of the molecules in the gap and this increases the rate of convection.

This invention relates to continuous casting of molten metal and, in particular, to a method for increasing the rate of heat transfer from the casting to the tubular, flowthrough, water-cooled mold ordinarily employed in continuous casting. 7

BACKGROUND OF THE INVENTION It is well known that, in continuous casting, there is a separation of the casting from the mold in the lower portion thereof as a result of contraction on cooling. The air gap thus created between the casting and the cooled mold wall materially reduces the transfer of heat from the former to the latter and thus delays solidification of the casting toward its center.

BRIEF SUMMARY OF THE INVENTION I have invented a method of increasing the heat transfer from casting to mold wall in the region where a separation therebetween exists. My method comprises maintaining a non-uniform electric field of high intensity, e.g., 10 kv./cm., across the gap. This causes increased movement of the molecules in the gap and the resulting increased circulation increases the rate of convection. To carry out my method, I employ a mold divided into two parts along a horizontal plane, and insulate the upper part from the lower. The upper part is grounded and the lower part is connected to a DC source of high voltage. The plane of division between the two mold parts is slightly below that at which the casting initially contracts enough to separate from the mold walls.

BRIEF DESCRIPTION OF THE DRAWING The single figure of the drawing is a central vertical section through a continuous-casting mold for carrying out my method and the casting formed therein.

DETAILED DESCRIPTION OF THE PREFERRED PRACTICE Referring now in detail to the drawing, a tubular flowthrough, water-cooled, mold 10 of any desired crossice sectional shape comprises an upper wall portion 11 and a lower wall portion 12. The upper portion is grounded by its connection to the usual supporting and reciprocating mechanism. The lower portion is mechanicall suspended from the upper portion by any suitable means but is electrically insulated therefrom by a ring or layer 13 of suitable material which has an interior facing 14 of refractory material such as alumina to protect it against the temperature of the metal in the mold.

The lower mold portion 12 is connected to a highvoltage D-C source 15 to establish a non-uniform, i.e., converging, electric field with a voltage gradient of about 10 kv./cm. across the space or gap 16 between the grounded casting 17 and the mold portion 12. When liquid metal, e.g., steel, is poured into the mold, the casting starts cooling from liquid to solid form at a level 18 spaced slightly down the mold height from the liquid level and shortly therebelow begins to contract from the mold wall at level 19.

Since the mold 10 surrounds the continuous casting 17 the electric field between the charged lower mold portion 12 and the grounded casting 17 is converging (i.e., non-uniform). The application of this non-uniform field causes increased movement 'of the molecules in the air gap, which can increase the heat transfer by convection by a factor of several times. These effects will occur whatever type of molecules are present in the air gap (i.e., liquid or gas; polar or non-polar), but will be increased by the presence of polar molecules produced by vaporization of the lubricant usually applied to the interior of the mold above the liquid level.

It should be evident that my invention has an important advantage in continuous-casting operations since the initial cooling of the casting in the mold to form a skin containing the still molten center is the bottle neck which limits the casting rate regardless of the size of the mold employed. The invention further makes it possible to achieve the skin formation in a shorter distance of travel down the mold.

Although I have disclosed herein the preferred embodiment of my invention, I intend to cover as well any change or modification therein which may be made without departing from the spirit and scope of the invention as set forth in the claim.

What is claimed is:

-1. A method of continuous-casting which comprises pouring molten metal into a tubular, flow-through, watercooled, mold and maintaining a non-uniform electric field across the gap between the casting and mold 'below the level of separation of the former from the latter by shrinkage on cooling.

References Cited UNITED STATES PATENTS 3,153,820 10/1964 Criner 164-273 X FOREIGN PATENTS 321,964 5/1957 Germany.

J. SPENCER OVERHOLSER, Primary Examiner I. E. ROETHEL, Assistant Examiner U.S. Cl. X.R. 16482, 122, 283 

